The present invention relates generally to plastic fasteners of the type that are adapted, for example, to attach tags to articles of commerce and relates more particularly to a novel method of manufacturing a plurality of said plastic fasteners as continuously connected fastener stock and to the continuously connected fastener stock thus made.
Plastic fasteners of the type comprising an elongated flexible filament having a first cross-bar at one end and a second cross-bar (or other enlargement, such as a paddle or a knob) at the opposite end are well-known and have been widely used in a variety of applications, such as in the attachment of merchandise tags to articles of commerce, in the attachment of buttons to garments, in the lasting of shoes, and in various packaging applications. Typically, such plastic fasteners are mass-produced by molding processes into either one of two different types of assemblies. One such assembly, an example of which is disclosed in U.S. Pat. No. 3,103,666, inventor Bone, issued Sep. 17, 1963 (which patent is incorporated herein by reference), is a clip-type assembly, said clip comprising a plurality of fasteners, each such fastener comprising a flexible filament having a first cross-bar at one end thereof and a paddle or second cross-bar at the opposite end thereof. The fasteners are arranged in a spaced, side-by-side orientation, with the respective first cross-bars parallel to one another and the respective paddles or second cross-bars parallel to one another, each of the first cross-bars being joined to a common, orthogonally-disposed runner bar by a severable connector. Adjacent second cross-bars or paddles also may be interconnected by severable connectors extending therebetween.
The aforementioned fastener clip is typically made by injection molding. Several commercial embodiments of the above-described fastener clip have been sold by the present assignee, Avery Dennison Corporation, as DENNISON(copyright) SWIFTACH(copyright) fastener clips.
A second type of fastener assembly is known as continuously connected fastener stock. In one type of continuously connected stock, the fastener stock is formed from two elongated, uniform and continuous side members coupled together by a plurality of cross-links equidistantly-spaced apart by a distance of 0.25 inch. Individual fasteners having an H-shape, often referred to as xe2x80x9cplastic staples,xe2x80x9d are dispensed from the fastener stock by cutting the side members at appropriate points between cross-links, thereby yielding individual fasteners having cross-bars of 0.25 inch in length. In another type of continuously connected stock, the fasteners comprise a flexible filament having a cross-bar at one end thereof and a paddle (or second cross-bar) at the opposite end thereof, the respective cross-bars and paddles of successive fasteners being arranged end-to-end and being joined together by severable connectors to form continuous, albeit non-uniform, side members.
An example of continuously connected fastener stock is disclosed in U.S. Pat. No. 4,039,078, inventor Bone, issued Aug. 2, 1977 (which patent is incorporated herein by reference). In said patent, the continuously connected fastener is described as being made by one of two different methods. The first of said two methods comprises extruding a continuous strip of plastic and then punching out or forming apertures in the strip in such a way as to leave only the side members and the cross-links in the strip, said side members and said cross-links being rectangular in cross-section. The other of said two methods comprises injection molding two or more separate lengths of the fastener stock and then joining together the lengths by applying heat to weld the respective side members together, said side members and said cross-links being circular in cross-section.
Neither of the two methods described above has received much, if any, commercial use in the manufacturing of continuously connected fastener stock.
Another example of continuously connected fastener stock is described in U.S. Pat. No. 4,462,784, inventor Russell, issued Jul. 31, 1984 (which patent is incorporated herein by reference). In said patent, the continuously connected fastener stock is made by a rotary extrusion process that involves the use of a rotating molding wheel whose periphery is provided with molding cavities that are complementary in shape to the molded fastener stock. To form fasteners, plastic is extruded into the cavities of the molding wheel, and a knife in substantially elliptical contact with the wheel is used to skive excess plastic from the molding wheel, leaving plastic only in the molding cavities. Following molding, the filament portions of the fasteners are typically stretched.
The aforementioned rotary extrusion technique has been used extensively by the present assignee in the manufacturing of continuously connected fastener stock. As can readily be appreciated, some advantages of the above-described rotary extrusion technique, as compared to the injection molding/welding technique described above, are that virtually any length of fastener stock can be obtained and that the post-molding welding step is eliminated.
However, one consequence of the rotary extrusion process described above, particularly the skiving step thereof, is that the first cross-bar, the filament, and the second cross-bar (or paddle) of each fastener are all flat on one side thereof, with the flattened sides of the first cross-bar, the filament and the second cross-bar all lying in the same plane (see e.g., FIG. 1B of U.S. Pat. No. 4,462,784). The other surfaces of the first-cross bar, the filament, and the second cross-bar (or paddle) conform to the shapes of the molding cavities and are typically not flat. For example, the other surface of the cross-bar (and the filament) is typically curved, thereby resulting in a cross-bar (and a filament) whose transverse cross-section has a shape resembling a semicircle or semi-ellipse. This property of the continuously connected stock of U.S. Pat. No. 4,462,784 of being shaped so as to be flat on only one side is apparently not shared by the continuously connected fastener stock of U.S. Pat. No. 4,039,078.
Tools (often referred to as xe2x80x9ctagging gunsxe2x80x9d or xe2x80x9cfastener attaching toolsxe2x80x9d) for dispensing individual fasteners from continuously connected fastener stock above are known, examples of such tools being disclosed in the following U.S. patents, all of which are incorporated herein by reference: U.S. Pat. No. 4,039,078, inventor Bone, which issued Aug. 2, 1977; U.S. Pat. No. 5,433,366, inventors Deschenes et al., which issued Jul. 18, 1995; U.S. Pat. No. 4,121,487, inventor Bone, which issued Oct. 24, 1978; U.S. Pat. No. 5,320,269, inventors Deschenes et al., which issued Jun. 14, 1994; U.S. Pat. No. 4,955,475, inventors McCarthy et al., which issued Sep. 11, 1990; U.S. Pat. No. 4,456,161, inventor Russell, which issued Jun. 26, 1984; U.S. Pat. No. 5,024,365, inventor Bourque, which issued Jun. 18, 1991; and U.S. Pat. No. 4,998,661, inventors Deschenes et al., which issued Mar. 12, 1991.
Such tools typically comprise a needle, the needle typically including a stem portion. The stem portion typically is generally cylindrical in shape and has a longitudinally-extending, cylindrically-shaped bore adapted to receive the first cross-bar of a fastener. In addition, said stem portion also typically has a longitudinally-extending slot adapted to permit the filament portion of a fastener to extend therethrough while the first cross-bar of the fastener is disposed in the longitudinal bore of the stem portion. The stem portion also typically has a tip adapted for insertion into a desired article of commerce. The needle also may include a base portion, said base portion being attached to the rear of the stem portion and being adapted to be removably received in the tool. The stem portion and the base portion may be a unitary structure or, as is more often the case, the base portion is insert-molded onto the rear end of the stem portion.
Such tools also typically comprise an ejector rod for ejecting a first cross-bar from the needle and into the article of commerce and may also include a knife or similar severing means for cutting the severable connector between the first cross-bar being dispensed and its adjacent first cross-bar and feeding means for advancing the assembly of fasteners in the tool so as to align the forwardmost first cross-bar with the needle.
One problem that has been noted by the present inventor with respect to the dispensing of continuously connected fastener stock of the type described in U.S. Pat. No. 4,462,784 using needles of the type described above is that, whereas the longitudinal bore and the longitudinal slot together have a symmetric transverse cross-sectional shape resembling an inverse lollipop (the longitudinal bore being circular in transverse cross-section, the longitudinal slot being rectangular in transverse cross-section and bisecting said longitudinal bore at the top thereof), the first cross-bar and the filament together have a xe2x80x9cdxe2x80x9d-shaped cross-section. Consequently, because a considerable portion of the transverse cross-sectional area of the bore is not occupied by the cross-bar, proper engagement of the cross-bar by the ejector rod and proper translational movement of the cross-bar through the length of the bore due to action of the ejector rod is not always achieved. This results in occasional malfunctioning of the tool.
It is an object of the present invention to provide a new method of manufacturing continuously connected fastener stock.
It is another object of the present invention to provide a method as described above that overcomes at least some of the problems described herein that are associated with existing methods for manufacturing continuously connected fastener stock.
According to one aspect of the invention, there is provided a method of manufacturing continuously connected fastener stock, said method comprising the steps of:
(a) providing a rotating molding wheel, said rotating molding wheel being provided with a peripheral impression comprising a pair of peripherally-extending side members interconnected by a plurality of cross-links;
(b) extruding molten plastic into the peripheral impression of said rotating molding wheel, with a layer of controlled film overlying the peripheral impression;
(c) allowing the molten plastic to solidify;
(d) using a knife in substantially elliptical contact with the peripheral impression to skive excess plastic from the rotating molding wheel, said knife having a bottom provided with a first cut-out portion aligned with one of said peripherally-extending side members so as to augment the transverse cross-sectional size thereof; and
(e) removing the continuously connected fastener stock thus formed from the rotating molding wheel.
Preferably, the peripheral impression is formed around the entire periphery of the rotating molding wheel, and the bottom of said knife is further provided with a second cut-out portion aligned with the other of said peripherally-extending side members so as to augment the transverse cross-sectional size thereof. In one embodiment, each of the peripherally-extending side members of said peripheral impression is generally uniform and semi-elliptical in transverse cross-section, each of said cross-links of said peripheral impression is generally semi-circular in transverse cross-section, and each of said first and second cut-out portions is complementarily shaped relative to its respective peripherally-extending side member of said peripheral impression so that each cross-link of the continuously connected fastener stock symmetrically bisects the side members of the continuously connected fastener stock.
In another embodiment, each of said peripherally-extending side members of said peripheral impression is generally rectangular in transverse cross-section, each of said cross-links of said peripheral impression is generally semi-circular in transverse cross-section, and each of said first and second cut-out portions is complementarily shaped relative to its respective peripherally-extending side member of said peripheral impression so that each cross-link of the continuously connected fastener stock symmetrically bisects the side members of the continuously connected fastener stock.
The present invention is also directed to a length of continuously connected fastener stock fabricated according to the above-described method.
According to another aspect of the invention, there is provided a length of continuously connected fastener stock, said length of continuously connected fastener stock comprising (a) first and second side members; and (b) a plurality of cross-links interconnecting said first and second side members, each of said cross-links having a flat surface and an arcuate surface; (c) wherein said first side member is shaped to extend transversely beyond said flat surface.
According to still another aspect of the invention, there is provided a length of continuously connected fastener stock, said length of continuously connected fastener comprising (a) first and second side members; and (b) a plurality of cross-links interconnecting said first and second side members, each of said cross-links having a flat surface; (c) wherein said first side member is shaped to extend transversely beyond said flat surface with an arcuate surface.
Additional objects, features, aspects and advantages of the present invention will be set forth, in part, in the description which follows and, in part, will be obvious from the description or may be learned by practice of the invention. In the description, reference is made to the accompanying drawings which form a part thereof and in which is shown by way of illustration specific embodiments for practicing the invention. These embodiments will be described in sufficient detail to enable those skilled in the art to practice the invention, and it is to be understood that other embodiments may be utilized and that structural changes may be made without departing from the scope of the invention. The following detailed description is, therefore, not to be taken in a limiting sense, and the scope of the present invention is best defined by the appended claims.